1. Field of the Invention
This invention relates to atomizers, in particular, atomizers for dispensing powders or liquids which are atomized by a stream of compressed air. Such atomizers may, for example, be used as medical atomizers or dispensing small quantities of medicaments.
2. Brief Description of Art
Most conventional atomizers of the above type operate continuously whether atomization is required or not. Strictly speaking, when such atomizers, frequently called nebulizers, are used in medical applications, atomization is only required during the inhalation phase of a breathing cycle so that a drug can be administered by deposition in the lungs. In practice a patient usually inhales for about 30 percent of the breathing cycle, consequently, use of a continuously operating atomizer results in a large proportion of the atomised drug being wasted.
Some designs of medical atomizer overcome such wastage by giving the patient a manual trigger to start the atomization when they begin to inhale. Such a manual trigger controlled type of atomizer is not satisfactory since the patient must coordinate inhalation with trigger operation.
In one conventional atomizer a gas duct leads qas under pressure to a gas exit, a reservoir for holding the substance to be atomised is formed around the base of the gas duct, and a sleeve placed around the gas duct defines a passageway through which the substance to be atomised may pass to at least one outlet. A fixed deflector in the form of a bar is disposed in line with the gas outlet so that gas issuing from the gas exit is deflected so as to pass over the outlet or outlets. The passage of gas over each outlet draws the substance to each outlet. The deflected gas atomizes the substance, and atomized particles of the substance are carried away by the stream of deflected gas, and are subsequently inhaled during the inhalation phase of the patient. Since the patient breathes air or gas in through the atomizer, but only inhales through part of the cycle, some of the drug is lost while the patient is not inhaling.
An example of such an atomiser system is to be found in EP-A-627,266 (Medic-Aid Limited).